Sahih Muslim 1080m
Ibn 'Umar (Allah be pleased with both of them) reported Messenger of Allah ﷺ as saying: The month (of Ramadan) may consist of twenty. nine days, and Shu'ba (one of the narrators) (gave a practical demonstration how the Holy prophet ﷺ explained to them) by unfolding his hands thrice and folding his thumb at the third turn. 'Uqba (one of the narrators in this chain of trans- mitters) said: I think that he said that the month consists of thirty days and unfolded his palm three times.
وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ عُقْبَةَ، - وَهُوَ ابْنُ حُرَيْثٍ - قَالَ سَمِعْتُ ابْنَ عُمَرَ، - رضى الله عنهما - يَقُولُ قَالَ رَسُولُ اللَّهِ ﷺ " الشَّهْرُ تِسْعٌ وَعِشْرُونَ " . وَطَبَّقَ شُعْبَةُ يَدَيْهِ ثَلاَثَ مِرَارٍ وَكَسَرَ الإِبْهَامَ فِي الثَّالِثَةِ . قَالَ عُقْبَةُ وَأَحْسِبُهُ قَالَ " الشَّهْرُ ثَلاَثُونَ " وَطَبَّقَ كَفَّيْهِ ثَلاَثَ مِرَارٍ .